In a digital computer system, several identical digital signal generators are usually used for generating synchronous and identical signals; the conventional method is to use a clock source as a common input for all such signal generators (as shown in FIG. 1), and each of them is to be counted for generating a synchronous signal. However, each signal generator has its particular characteristics, i.e., when each signal generator starts to count, the time required to count might have more or less of a difference of about 1-3 clock signals; further, as soon as the frequency of the clock source is higher, such difference will also be greater. Moreover, when the voltage level of the clock is unstable, a non-synchronization might take place. Therefore, an automatic correction means has to be provided, otherwise, the stability of the whole system would be reduced considerably.